If you want to make sure your letter is received as quickly as possible, follow the instructions below. After two attempts by the sender, I received a letter written in poor script with no zip code and violated most of the USPS guidelines. In addition, I was interested if there should be a comma after the city name. The following information was obtained from the Postal Addressing Standards

A standardized address is one that is:
Fully spelled out or
Abbreviated by using the Postal Service standard abbreviations or
As shown in the current Postal Service ZIP+4 file.

Look up a Zip Code - USPS It's easy, just enter the address here and the USPS program will give you the correct information.

Address Checker Verifies & corrects U.S. addresses, Displays the address type, time zone, County, Census Tract & Block, Congress District & Representative, Upper and Lower State Legislative districts. (not a USPS website)

Attention Line

The Attention Line is placed above the Recipient Line, that is, above the name of the firm to which the mailpiece is directed.

Address unit designators, e.g., Apt number

Secondary address unit designators, such as APARTMENT or SUITE, are required to be printed on the mailpiece for address locations containing secondary unit designators. The preferred location is at the end of the Delivery Address Line. The pound sign (#) should not be used as a secondary unit designator if the correct designation, such as APT or STE, is known or is shown in the ZIP+4 file.

If all Delivery Address Line information cannot be continued in the Delivery Address Line above the city, state, and ZIP Code, place secondary address information on the line immediately above the Delivery Address Line.

              Common Approved Abbreviations            All Approved Abbreviations

Format

Format all lines of the address with a uniform left margin.

Address aligned in a block style.

Uppercase letters are preferred on all lines of the address block.

Lowercase letters in various type styles are acceptable provided they meet postal guidelines for OCR readability.

Format the Last Line with at least one space between the city name, two–character state abbreviation, and ZIP+4 Code.

Two spaces are preferred between state abbreviation and zip code.

Punctuation

With the exception of the hyphen in the ZIP+4 Code, it is preferred that punctuation be omitted in the delivery address block.

Spelling of City Names

Spell city names in their entirety.

When abbreviations must be used due to labeling constraints, use only the approved 13–character abbreviations provided in the City State file.

Note: Normally, the abbreviations follow the logic of using existing abbreviations, such as for suffix or directional words.